• Journal of Dental Rehabilitation and Applied Science
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• v.30 no.2
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• pp.145-151
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• 2014

Purpose: The purpose of this study was to investigate the microleakage in class II cavity resin restorations used with resin-modified glass ionomer (RMGI) lining material depending on two different applying methods; classical delivery method using a dental explorer and a specially designed rotating bur. Materials and Methods: A total thirty-six extracted teeth were prepared with a class II proximal box, and randomly divided into three groups: 1) control group with no lining added and the proximal box restored (Group I), 2) the second group used RMGI as a lining material which was spread with an explorer (Group II), 3) the third group used a specially designed rotating bur to thin out RMGI (Group III). All teeth were restored with the same manner using incrementally placed resin composite. All 36 teeth were prepared and sectioned for the dye penetration test, and observed with a stereomicroscope for scoring the dye penetration. Results: When RMGI liners were used, both groups using an explorer and the special bur with the liner had significantly less microleakage than the control group with no liner (P < 0.05). The 50% of the group with RMGI liner using the bur showed no microleakage under a dye penetration test whereas all the teeth in control group showed microleakage of different degrees. However, there was no statistically significant difference between Group II and Group III. Conclusion: RMGI is an effective lining material to decrease microleakage in class II composite resin restorations regardless of applying methods.

• Restorative Dentistry and Endodontics
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• v.31 no.5
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• pp.337-343
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• 2006

The purpose of this study was to estimate the relation between techniques used for microleakage from dye penetration and for marginal adaptation from SEM evaluation of the restoration. Using high speed #330 bur class V cavities ($4{\times}3{\times}1.5 mm$ around CEJ) were prepared on the buccal surface of 20 extracted human molars. Six dimples as reference points for SEM and dye penetration evaluation were made with 1/2 round bur. Cavity was bulk filled with microhybrid composite resin (Esthet X) and all-in-one adhesive (Xeno III). Teeth were stored in saline solution for one day, after then, they were finished and polished using Sof-Lex system. Fifty percent silver nitrate dye solution was used for the evaluation of microleakage and resin replica was used for marginal adaptation. All of these were done after 1000 times thermocycling between 5 and $55^{\circ}C$. Vertical sections were made through three dimples of restoration to obtain samples for the evaluation of dye penetration and inner marginal adaptation. Outer adaptational estimation was done with an intact restoration before sectioning. Dye penetration was determined in three degrees and percentage of outer and inner leaky margin was estimated from SEM image The data were analysed statistically: Spearman's rho test were used to check relationships between two methods. The result were as follows : 1. There were significant relationships between degree of dye penetration and inner and outer marginal adaptations each (p < 0.01). 2. However, there was no significant relationship between the results or inner and outer marginal adaptation. Within the results of this study, relationship between the percentage of marginal adaptation and microleakage shows significant relationship. However, inner and outer marginal adaptation did not show any significant relationship mutually.

• The Korean Journal of Malacology
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• v.23 no.2
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• pp.209-216
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• 2007

The ovarian structure and ultrastructural changes in germ cells during oogenesis of the spiny top shell, Batillus cornutus, have been investigated by light and electron microscopic observations. Specimens of the spiny top shell were collected from the subtidal zone of Wando, south coast of Korea. Spiny top shell was dioecious. The ovary was located on the surface of the hepatopancreas in the spiral posterior region. The ovary had greenish color in the gonadal mature season. The ovary comprised many ovarian lobules, and the ovarian lobule consisted of connective mesenchymal tissue and epithelial cells. Oogonium had a large nucleus with nucleolus of high electron density. In previtellogenic oocyte, small yolk granules of low electron density were scattered in the cytoplasm. Oocytes in the initial vitellogenic stage were connected with the ovarian lobule by egg stalk. The result of TEM observations showed that initial vitellogenic oocyte contained well-developed Golgi complex, endoplasmic reticula, tubular mitochondria and numerous yolk granules of various electron densities and sizes. The electron density, size and quantity of yolk granules which were distributed in the active vitellogenic oocyte were increased compared to the previous stage. Thickness of egg envelope in the late active vitellogenic oocyte was approximately 4.4 $[\mu}m$. Cytoplasm of ripe oocyte was filled with proteid yolk globules of high electron density and lipid yolk globules of low electron density. In this stage, the thickness of egg envelope was approximately 6.5 ${\mu}m$.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.48 no.7
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• pp.76-81
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• 2011

A new via cutting structure in 2-layer DRAM package substrate has been fabricated to lower its power distribution network(PDN) impedance. In new structure, part of the via is cut off vertically and its remaining part is designed to connect directly with the bonding pad on the package substrate. These via structure and substrate design not only provide high routing density but also improve the PDN impedance by shortening effectively the path from bonding pad to VSSQ plane. An additional process is not necessary to fabricate the via cutting structure because its structure is completed at the same time during a process of window area formation. Also, burr occurrence is minimized by filling the via-hole inside with a solder resist. 3-dimensional electromagnetic field simulation and S-parameter measurement are carried out in order to validate the effects of via cutting structure and VDDQ/VSSQ placement on the PDN impedance. New DRAM package substrate has a superior PDN impedance with a wide frequency range. This result shows that via cutting structure and power/ground placement are effective in reducing the PDN impedance.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.4
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• pp.249-256
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• 2017

Premixed combustion has many advantages, including low CO and NOx emissions and a small combustor volume. These characteristics allow a compact design and wide application to condensing boilers with high thermal efficiencies. This study focused on the combustion characteristics in a premixed combustion burner using metal fiber and a throttle body. The results showed that a blue flame was found to be very stable at a heating load of 6,250-25,000 kcal/h when implementing the proper metal fiber, baffle plate, and throttle body. The NOx emission was less than 11 ppm under an equivalence ratio of 0.724-0.795, and the CO emission was less than 50 ppm under the same equivalence ratio. The thermal efficiency, which is a very important index when condensing a gas boiler, was observed to be above 96.3％ under an equivalence ratio of 0.750.

• The Journal of the Convergence on Culture Technology
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• v.9 no.4
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• pp.229-238
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• 2023

This study is to identify marketing methods that are different from the existing ones on the Metaverse platform, where new business models and industrial ecosystems are being formed. The purpose of this study is to identify how brand marketing methods are differentiated according to the type of metaverse and the characteristics of the main users who use metaverse. The research method was a case analysis method, and Roblox, which currently has the largest number of active users, was selected. We closely analyzed how Nike and Gucci brands market by reflecting the characteristics and consumption patterns of Alpha Generation and Generation Z, the main users of Roblox. The results of the analysis are as follows. First, it is approaching with enjoyable content, including games, rather than direct marketing. Second, the content provided contains the brand's story and philosophy. Third, it takes a method of linking virtual and reality. Lastly, through Metaverse, Brands are identifying the tastes of future potential customers and collecting data for customized services.

• Journal of the korean academy of Pediatric Dentistry
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• v.50 no.1
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• pp.65-74
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• 2023

This study compared the surface roughness and microbial adhesion characteristics of Omnichroma, a novel composite resin developed using "smart chromatic technology", with those of two other conventional composite resins with different filler compositions. A total of 144 specimens were fabricated using 3 types of composite resins: Omnichroma (nano-spherical), Filtek Z350XT (nanofill), and Tetric N-Ceram (nanohybrid) and, divided into 3 groups of 48. Finishing was performed using tungsten carbide burs. Specimens were then divided into 3 subgroups using different polishing methods: Control, SofLex, and PoGo. Surface roughness was analyzed quantitatively and qualitatively using an atomic force microscope and a scanning electron microscope. Microbial adhesion was assessed by culturing Streptococcus mutans on the specimens for 24 hours and then measuring colony-forming units attached to the upper surface. The surface roughness (Ra) of Omnichroma was 0.123 ㎛ after finishing, and it exhibited a smooth surface compared to the other resins. However, after polishing, there were no significant differences in the surface roughness between the three composite groups, regardless of the polishing methods. The surfaces of the Control subgroups were significantly rougher than those of the SofLex subgroups in all 3 composite groups. However, except for Tetric N-Ceram, there were no significant differences between the Control and PoGo subgroups in the other composite groups. Microbial adhesion assessment showed no significant differences between any of the 3 composite resin subgroups; however, Omnichroma exhibited higher microbial adhesion than the other two composites. No significant correlation was observed between surface roughness and microbial adhesion.

• Journal of Internet Computing and Services
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• v.19 no.5
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• pp.89-96
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• 2018

In online communities, a large number of participants can exchange their opinion using replies without time and space restrictions. While the online space provides quick and free communication, it also easily triggers unnecessary quarrels and conflicts. The network established on the discussion participants is an important cue to analyze the confrontation and predict serious disputes. In this paper, we present a quantitative measure for polarity observed on the discussion network built from reply exchanges in online communities. The proposed method uses the comment exchange information to establish the user interaction network graph, computes its maximum spanning tree, and then performs vertex coloring to assign two colors to each node in order to divide the discussion participants into two subsets. Using the proportion of the comment exchanges across the partitioned user subsets, we compute the polarity measure, and quantify how discussion participants are bipolarized. Using experimental results, we demonstrate the effectiveness of our method for detecting polarization and show participants of a specific discussion subject tend to be divided into two camps when they debate.

• Economic and Environmental Geology
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• v.56 no.3
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• pp.343-363
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• 2023

Sulawesi island, as a global producer of nickel resources, is leading the rapid growth of nickel industry of Indonesia. Nickel laterite deposits in Sulawesi was formed by lateritization of the world-scale East Sulawesi Ophiolite (ESO) under the active tectonic setting and tropical rainforest climate. In this paper, exploration cases for nickel laterite deposits in five regions of Sulawesi are reported. Regional characteristics on nickel laterite deposits in Sulawesi are understood based on various exploration activities such as outcrop, trench and pit survey, petrological observation, geochemical analysis, and interpretation of drilling data, etc.. In the northeastern part of 'Southeast-Arm', which is a strategic location for nickel industry of Indonesia, ESO is extensively exposed to the surface. In the Morombo and Morowali regions, typical high-grade saprolite-type orebodies with a thickness of 10 to 20 m occur. The cases showed that topographic relief tends to regulate Ni-grade distribution and orebody thickness, and that high grade intervals tend to occur in places where joints and garnierite veins are dense. In the Tinanggea and South Palangga regions in the southern part of the Southeast-Arm, overburden composed of Neogene to Quaternary deposits is a major factor affecting the preservation and profitability of nickel laterite deposits. Despite the overburden, high-grade saprolite-type orebodies composed of Ni-bearing serpentine with garnierite veins occur in a thickness of around 10 m to secure economic feasibility. In contrast, in the Ampana region in the northern part of 'East-Arm', low-grade nickel laterite deposits with immature laterite profile was identified, which is thought to be the result of active denudation due to tectonic uplift. Exploration cases in this paper will help to understand characteristics and controlling factors on nickel laterite deposits in Sulawesi, Indonesia.

• Economic and Environmental Geology
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• v.32 no.5
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• pp.435-444
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• 1999

The antimony deposits of the Hyundong mine, located in the northeastern part of the Sobaegsan massif, occur as hydrothermal quartz+carbonate veins and stockworks which fill the fault fractures developed in Precambrian metamOlphic rocks (mainly, granitic gneiss). Hydrothermal alteration occurs commonly in the vicinity of mineralized veins and is characterized by sericitization and silicification. A K-Ar age of alteration sericite is 139.2$\pm$ 4.4 Ma, implying the early Cretaceous age of mineralization, possibly in association with intrusion of nearby acidic dikes (mainly, quartz porphyry). The hydrothermal mineralization occurred in five mineralization stages. These are: (I) stage I, characterized by deposition of chalcedonic quartz; (2) stage II, deposition of quartz with base-metal sulfides and stibnite; (3) stage III, deposition of quartz and carbonates (calcite, dolomite, ankerite, rhodochrosite) with various antimony-bearing minerals such as stibnite, polybasite, berthierite, native antimony, gudmundite and ullmannite; (4) stage IV, deposition of calcite with stibnite; and (5) stage V, deposition of barren calcite. Antimony occurs mostly as stibnite within stages II to IV veins, which has various habits including disseminated, veinlets and euhedral coarse crystals. Fluid inclusion studies indicate that hydrothermal mineralization at Hyundong occurred from the fluids with temperature and salinity of $330^{\circ}$C to 120 and 5.3 wI. % equiv. NaCI. The temperature and salinity of ore fluids systematically decreased with elapsed time in the course of mineralization, possibly due to the influx of larger amounts of meteoric groundwater. The deposition of antimony-bearing minerals occurred at low temperatures «$250^{\circ}$C), mainly due to the cooling and dilution of fluids. Based on the evidence of fluid boiling during the early stage II mineralization, the mineralization occurred under low pressure conditions (about 80 bars, corresponding to depths of about 350 m under hydrostatic pressure regime). Thermodynamic considerations of ore . mineral assemblages indicate that antimony deposition also occurred as the results of decreases in temperature and sulfur fugacity of hydrothermal fluids. Calculated sulfur isotope composition of ore fluids ($\delta^{34}S_{\Sigma s}$=5.4 to 7.8$\textperthousand$) indicates an igneous source of sulfur.